开云体育

No, I've not measured a high impedance 'scope probe on a VNA (which is typically intended for 50R systems). I'm away from home on business so won't be doing so any time soon (I have a number of VNAs).

If it helps, look at the Tek datasheet in the link below. It shows Rp vs frequency for a typical 100MHz x10 scope probe. The input Rp for the 10073C will be fairly similar vs frequency. It will fall

Jeez, I've just read all the recent replies. Have none of you ever measured a x10 scope probe before? You can't assume the Cp will remain at 12pF up at UHF. Also, the Rp will fall with increasing

No I'm not counting the capacitance twice. Rp is a measure of parallel resistance not parallel capacitance. At 400-500MHz, the 10073C will load a circuit in a similar way to the loading caused by a

You saved my day... Raymond

Hi Robert, Is that meant as an answer to my question? I'd say (HP spec) Rp = 2.2MOhm, Cp = 12pF, resulting in |Xc| less than 30Ohm @ 500MHz, or no? I'm confused... Raymond

Crossed with Raymonds reply. I was assuming the probe input capacitance was 12pF. Seems odd to split the reactive impedance. Robert.

Hi Gianni, I'm one of the many that have admired your beautiful books from the beginning but haven't posted about that. As regards your above post, I'm not sure what you mean by "both": Two NiCds?

But you have Rp and 7pF probe capacitance. That is counting the input capacitance twice.

Not relevant for the discussion but what's the math behind that? HP 10073C data 2.2MOhm // 12pF. Raymond

I have one E4406A with the same problem. I didn't disassemble it. I saw comments that could be the power source. Do I check the power source directly? It has the same characteristic sound. And it does

It would have been interesting to measure the lead levels in consumer electronics techs 50 years ago (and still today) who lit cigarettes with soldering irons. Adding lead to that menagere of poisons

The R2 value of 60R is the equivalent Rp (parallel resistance) of the 10073C at about 500MHz. If you measured the 10073C with an impedance analyser down at low frequencies (eg in the kHz region) Rp

Hi, Where is R2 derived from? The 10073C input resistance is 2M2 not 60R. You have included the capacitance so can't be that unless you are double accounting? What is the delta at 350MHz? Robert.

Of course, what this means in reality, is that you can expect to achieve slightly confusing results if you used this Tee setup to test the 10073C against a near perfect Zo probe for frequency response

If you aren't happy/familiar with a HB simulation, then see below for a SPICE simulation. The result is the same although the SPICE simulation will show how it settles in steady state. So it may be

I don't know if this helps, but look at the simulation below. This assumes a dielectric constant of 2 for the BNC Tee and a distance of 46mm between the probes. The simulation is a harmonic balance

My had both, but I concluded that the big one (HP-67 style) was not used, so I changed only that on board and it works.

JMR said: "If the 3.5GHz 'known good probe' probe is a passive Zo probe, it might look like 500R in parallel with 1pF up at UHF. By contrast, a 10073C will typically look like about 60R in parallel

I'm not absolutely sure of the details, but as I recall, the 8568A (and 8566A) to "B" conversions changed it from an off-board 3-cell NiCd HP35 calculator-style pack, to a single 3V Li-ion cell